With the development of semiconductor technologies, backside-illuminated complementary metal oxide semiconductor (CMOS) image sensors are more and more adopted. Backside-illuminated CMOS image sensors have light incident from backside which enters into the light-sensing element first. This configuration can avoid the affect from circuit wiring layers and transistors of traditional CMOS image sensor configuration, and can greatly increase the efficiency of light, improve the photographing effect in a low illumination condition such that the focusing ability and image quality both improved greatly in the low illumination condition.